Yet another serve question - stance

Is there anything wrong with a cross step during the serve? I feel the weight transfer is really OK (which does not necessarily mean it is in fact correct). What happens is that, right before contact, my back foot steps slightly ahead of my front foot, which gives me an upward and, mostly, forward thrust, which puts me quite inside the court for the volley. DOUBLE FAULT!!! you yell. But I do stand a few inches behind the baseline for the toss. I do indeed feel that, in a way, I run into the court, but that's sort of the idea.
I'm asking you this because I took a few lessons with an instructor - a baseline claycourter - who really insisted I changed my serve, tossing more to the back of my head and not thrusting myslef into the court. I felt like he was getting me to do what he does. It seemed he disliked my style, not my mechanics. It kind of messed up a serve that I considered quite efficient. Thus my endless questions :wink: .